Tropical Storm FOUR Advisory 29 Ιούν.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 04W (FOUR), LOCATED APPROXIMATELY 373 NM
NORTH-NORTHWEST OF KAYANGEL, HAS TRACKED NORTHWESTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS SITUATED JUST
TO THE WEST OF A 281800Z PGTW SATELLITE FIX WITH FAIR CONFIDENCE. THE
INTENSITY OF 25 KNOTS IS CONSISTENT WITH RECENT SUBJECTIVE DVORAK
INTENSITY ESTIMATES FROM PGTW AND KNES AND FURTHER SUPPORTED BY
EARLIER ASCAT DATA INDICATING 20-25 KNOT WINDS NEAR THE CENTER OF
CIRCULATION. TD 04W IS TRACKING NORTHWESTWARD ALONG THE PERIPHERY OF
A SUBTROPICAL STEERING RIDGE SITUATED TO THE NORTH AND EAST. FLARING
DEEP CONVECTION HAS PERSISTED WITHIN THE SOUTHWESTERN QUADRANT OF THE
LOW LEVEL CIRCULATION CENTER (LLCC) IN THE PRESENCE OF MODERATE
NORTHEASTERLY VERTICAL WIND SHEAR (VWS). THE SEA SURFACE TEMPERATURE
IN VICINITY OF THE LLCC IS VERY SUPPORTIVE AT 29 TO 30 DEGREES
CELSIUS.
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 04W IS EXPECTED TO CONTINUE TRACKING NORTHWESTWARD IN THE
NEAR TERM UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGING TO
THE NORTH AND EAST. PERSISTENT VWS SHOULD OFFSET THE FAVORABLE
INFLUENCES OF PASSAGE OVER VERY WARM WATER AND WESTWARD DIFFLUENCE
ALOFT, YIELDING A SLOW INTENSIFICATION RATE. NUMERICAL MODEL GUIDANCE
DIVERGES REGARDING THE OVERALL SCENARIO, WITH A GROUPING CONSISTING
OF THE GFS, HWRF AND NAVGEM SOLUTIONS REFLECTING A TRACK TOWARD
SOUTHERN TAIWAN OR FARTHER TO THE SOUTH AND THE UKMET AND ECMWF
PREDICTING A TRACK TOWARD NORTHER TAIWAN OR FARTHER TO THE NORTH AND
EAST. THE FIRST 72 HOURS OF THE CURRENT FORECAST FAVORS THE SOUTHERN
GROUPING, CONSISTENT WITH THE MODEL CONSENSUS.
   C. THE TRACK OF TD 04W IN THE EXTENDED RANGE IS HIGHLY UNCERTAIN,
WITH MODEL SOLUTIONS RANGING FROM A STRAIGHT-RUNNING TRACK INTO
NORTHERN PORTION OF THE SOUTH CHINA SEA TO A RECURVATURE TO THE EAST
AND NORTH OF TAIWAN. GIVEN THAT TD 04W IS EXPECTED TO INTENSITY,
ALBEIT SLOWLY, AND THE SUBTROPICAL STEERING RIDGE IS EXPECTED TO
NEARLY MAINTAIN ITS CURRENT POSITION AND ORIENTATION THROUGHOUT THE
FORECAST PERIOD, CONTINUED MOTION TOWARD THE NORTHWEST NEAR THE
MIDDLE OF THE MODEL GUIDANCE ENVELOPE IS CONSIDERED MOST PROBABLE.
THUS, THE CURRENT TRACK FORECAST IS POSITIONED NEAR THE MULTI-MODEL
CONSENSUS FOR THE EXTENDED PERIOD, BUT WITH LOW CONFIDENCE. VWS IS
EXPECTED TO CONTINUE INFLUENCING THE SYSTEM EVEN INTO THE EXTENDED
RANGE AND LAND INTERACTION IS ALSO DISTINCTLY POSSIBLE, SO SLOW
INTENSITY CHANGE IS EXPECTED THROUGHOUT.//
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